Update readme.md

Updated feature flag.

x-pack/plugins/stack_alerts/public/alert_types/geo_threshold/readme.md

@@ -22,7 +22,7 @@ the next step to the bottom of the file (or really anywhere) and save. For more
 on different config modifications or on how to make production config modifications,
 see [the current docs](https://www.elastic.co/guide/en/kibana/current/settings.html)
 - Set the following configuration settings in your `config/kibana.yml`:
-`xpack.stack_alerts.enableGeoAlerting: true`
+`xpack.trigger_actions_ui.enableGeoTrackingThresholdAlert: true`
 
 ### 2. Run ES/Kibana dev env with ssl enabled
 - In two terminals, run the normal commands to launch both elasticsearch and kibana but